Acid-base reaction
The Swede Svante Arrhenius used the term acid to describe a substance that dissolves in water to produce H3O+. Arrhenius bases dissolve in water to produce OH–. In 1923 Johannes Bronsted (Danish) and Thomas Lowry (English) proposed independently the more general and more useful definitions that focus on the role of the proton (H+) in acidity and basicity.
Acids are proton donors.
Bases are proton acceptors.
Bronsted-Lowry acids and bases react by proton transfer.
As seen above, water can act either as an acid or as a base. H3O+ and OH– are present in very low concentrations in pure water, due only to reaction of water with itself.
H2O (acid) + H2O (base)
Acids that are stronger than water donate a proton to water, giving rise to H3O+.
Thus the concentration of H3O+ in their solutions is higher than water. these acids are both Bronsted and Arrhenius acids.
HA (acid) + H2O (base)
Bases that are stronger than water accept a proton from water, giving rise to OH– .
Thus the concentration of OH– in their solutions is higher than water. these acids are both Bronsted and Arrhenius bases.
B (base) + H2O (acid)
Acids are proton donors.
Bases are proton acceptors.
Acids can be cations (NH4+, H3O+), molecules (CH3CO2H, H2O) or anions (H2PO4–).
Bases can be molecules (NH3, H2O) or anions (CH3CO2– , OH–).
These acids and bases may be referred to as Bronsted-Lowry acids and bases to distinguish them from an even more general class of acids that is introduced in more advanced chemistry courses.
Bases can be molecules (NH3, H2O) or anions (CH3CO2– , OH–).
These acids and bases may be referred to as Bronsted-Lowry acids and bases to distinguish them from an even more general class of acids that is introduced in more advanced chemistry courses.
Bronsted-Lowry acids and bases react by proton transfer.
As seen above, water can act either as an acid or as a base. H3O+ and OH– are present in very low concentrations in pure water, due only to reaction of water with itself.
H2O (acid) + H2O (base)
H3O+(aq) + OH–(aq)
Acids that are stronger than water donate a proton to water, giving rise to H3O+.
Thus the concentration of H3O+ in their solutions is higher than water. these acids are both Bronsted and Arrhenius acids.
HA (acid) + H2O (base)
H3O+(aq) + A–(aq)
Bases that are stronger than water accept a proton from water, giving rise to OH– .
Thus the concentration of OH– in their solutions is higher than water. these acids are both Bronsted and Arrhenius bases.
B (base) + H2O (acid)
BH+(aq) + OH–(aq)